1. Technical Field
The present invention relates to a communication device and the like including a main processing unit that perform a process, a sub-processing unit that performs a process with power lower than that of the main processing unit, and a shared memory to which both of the main processing unit and the sub-processing unit are accessible.
2. Related Art
In the related art, in a communication device such as a printer, a main processing unit and a sub-processing unit operating with power lower than that of the main processing unit are provided, and the supply of power to the main processing unit is stopped when predetermined conditions are satisfied, to reduce power consumption in the whole of the communication device.
In such a communication device, when the sub-processing unit (sub-device unit) receives data or the like to be processed in the main processing unit (main device unit), the supply of power to the main processing unit is restarted such that the data is processed in the main processing unit (e.g., see Japanese Patent No. 4271520).
Among the processes performed by the main processing unit are processes performed at predetermined time intervals, for example, a mail reception check process. For example, in Japanese Patent No. 4271520, a technique is disclosed in which the interval of the mail reception check is succeeded from the main processing unit to the sub-processing unit, and the mail reception check process is performed whenever the mail reception check interval elapses.
In the technique, the sub-processing unit succeeding the mail reception check interval measures the mail reception check interval again from the time point after the succeeding to start the mail reception check processing. For this reason, the mail reception check process is not performed at a time point (initially planned time point) which is initially planned in the main processing unit. For example, depending on the processes, it may be important to perform a process at the initially planned time point (or around the planned time point). In such a process, it is a great problem that the process is not performed at the initially planned time point or around the time point.
On the other hand, it is conceivable that a remaining time to the initially planned time point is succeeded to the sub-processing unit when the main processing unit is stopped. However, in the main processing unit, generally, an interface acquiring the remaining time from the timer which is counting the time is not provided, and it is time-consuming and difficult to acquire the remaining time in the main processing unit. Even if the remaining time can be acquired, time is necessary to succeed the remaining time from the main processing unit to the sub-processing unit. Accordingly, there is a problem that the time cannot be accurately measured in the sub-processing unit.